Edward Snowden cost British taxpayer money, says Theresa May

Asked by Michael Ellis, a Conservative MP, if there had been "financial consequences", Mrs May replied: "If work has to be done in order to try to mitigate the impact then that takes resource."

It is understood the security services MI5 and MI6 have had to mothball or abandon "safe houses" whose locations were revealed by the Snowden documents, because they were considered compromised.

The impact will also have had a wide-ranging effect on staffing hours and deployment.

Edward Snowden has sought political asylum in Russia

Outside the committee, Mr Ellis said: "It is clear to me the damage Snowden has done is monumental.

"Not only has he jeopardised national security by his leaks, but he has also put people at risk and it is clear that he has also caused considerable financial loss."

David Cameron: Guardian Snowden leaks 'damaged national security'

Quarter of criminals being watched by GCHQ have gone off radar since Snowden leaks

Snowden stole tens of thousands of files from systems at the US National Security Agency in 2013 from which the techniques and methods of it and GCHQ were exposed in a series of articles in The Guardian newspaper.

In the wake of the scandal, Sir John Sawers, then Chief of MI6, said Britains enemies would be rubbing their hands with glee.

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Edward Snowden cost British taxpayer money, says Theresa May